Image forming with tilting register rollers to correct alignment

Abstract

In a copying machine inclucing paired register rollers which are driven after a front end of a paper supplied from a paper supply cassette comes in contact with the paired register rollers and is aligned and a copying unit for copying a document image on the paper fed by the paired register rollers, the paired register rollers are mounted on a frame via self-aligning bearings, two paper front detecting sensors are disposed on both sides of the center of a feeding path between the paired register rollers and the copying unit, the direction and angle of tilt of the paper held by the paired register rollers with respect to the feeding direction of the paper are detected based on a difference between timings at which the two sensors are turned on, and the paired register rollers are tilted in a direction opposite to the detected direction by the detected angle, thus correcting the tilt of the paper.

What is claimed is: 
     
       1. An image forming apparatus comprising: means for forming an image on an image forming medium;   feeding means for feeding and supplying said image forming medium to said image forming means;   means for detecting a tilting of said image forming medium fed by said feeding means, in relation to the feeding direction; and   means for tilting said feeding means on a plane on which said image forming medium is fed, according to the tilting detected by said detection means, to correct the tilting of said image forming medium.   
     
     
       2. An apparatus according to claim 1, in which said detection means includes two image forming medium detecting means arranged in a direction perpendicular to the feeding direction of said image forming medium and arithmetic operation means for deriving a tilt based on a difference between timings at which said two detecting means are turned on. 
     
     
       3. An apparatus according to claim 2, in which said arithmetic operation means includes means for detecting the direction of the tilt according to which of said two detecting means is first turned on and detecting the angle of tilt based on the difference between the timings at which said two detecting means are turned on. 
     
     
       4. An apparatus according to claim 3, in which said tilt correction means includes means for tilting said feeding means in a direction opposite to the detected direction of the tilt by the detected angle of tilt. 
     
     
       5. An apparatus according to claim 1, in which said detection means includes two image forming medium detecting means arranged in a direction perpendicular to the feeding direction of said image forming medium and means for detecting the direction of tilt according to which of said two detecting means is first turned on. 
     
     
       6. An apparatus according to claim 5, in which said tilt correction means includes means for tilting said feeding means in a direction opposite to the detected direction of the tilt in a period from the time when one of said detecting means is turned on until the other detecting means is turned on. 
     
     
       7. A method for correcting directional misalignment of an image forming medium in an image formation device for forming an image on the image forming medium, while the image forming medium is being fed by paired rollers disposed in front of said image forming means, said method comprising the steps of: interrupting the rotation of said paired rollers after said image forming medium is held therebetween;   detecting the direction and angle of a tilt of said image forming medium which is held between said paired rollers;   tilting said paired rollers in a plane on which said image forming medium is held and in a direction opposite to a detected direction of tilt and by the detected angle of tilt; and around a point located on a line along an axial direction of the paired roller, so as to correct directional misalignment of said image forming medium; and   restarting rotation of said paired rollers, to feed said image forming medium into said image forming means.   
     
     
       8. An image forming apparatus comprising: paired rollers for holding and feeding a supplied image recording medium;   image forming means for forming an image on said image recording medium fed by said paired rollers;   detection means disposed between said paired rollers and said image forming means, for detecting directional misalignment of said image forming medium; and   correction means for tilting the paired rollers holding and feeding said image forming medium in a direction opposite to the directional misalignment and around a point located on a line along an axial direction of the paired rollers, so as to correct directional misalignment of said image forming medium based on an output from said detection means.   
     
     
       9. An apparatus according to claim 8, in which said paired rollers are mounted on a housing of said device via self-aligning bearings so as to be tilted in an image forming medium feeding plane, and said correction means includes means for tilting said paired rollers in a direction opposite to the direction of the detected directional misalignment by an angle of the detected directional misalignment. 
     
     
       10. An apparatus according to claim 9, in which said tilting means includes means disposed along said housing, for moving one-end portions of said paired rollers back and forth in the feeding direction according to an output of said detection means. 
     
     
       11. An apparatus according to claim 8, in which said detection means includes two medium front end detecting sensors disposed parallel to said paired rollers and means for detecting a direction of the directional misalignment according to which of said two sensors is first turned on and deriving an angle of the directional misalignment based on a difference between timings at which said sensors are turned on. 
     
     
       12. An apparatus according to claim 8, in which said detection means includes two medium front end detecting sensors disposed parallel to said paired rollers and means for detecting a direction of the directional misalignment according to which one of said two sensors is first turned on. 
     
     
       13. An apparatus according to claim 12, in which said correction means includes means for tilting said paired rollers in a direction opposite to the detected direction in a period from the time when one of said sensors is turned on until the other sensor is turned on. 
     
     
       14. An apparatus according to claim 8, wherein said correction means comprises means for tilting said paired rollers on a plane in which said image recording medium is held. 
     
     
       15. A method for correcting directional misalignment of an image forming medium in an image formation device for forming an image on the image forming medium, while the image forming medium is being fed by paired rollers disposed in front of said image forming means, said method comprising the steps of: interrupting rotation of said paired rollers after the image forming medium held therebetween is detected as having an angle of tilt;   tilting said paired rollers on a plane on which the image forming medium is held and in a direction opposite to the detected direction of tilt around a point located on a line along an axial direction of the paired rollers;   stopping tilting of said paired rollers when the image forming medium is detected as no longer being tilted; and   restarting rotation of said paired rollers, to feed said image forming medium into said image forming means.